1. Field of the Invention
The present invention generally relates to an image forming system and, more particularly, to an image forming system including a plurality of image forming apparatuses selectively connected to a host computer.
2. Description of the Related Art
Generally, an image forming apparatus such as a printer is connected to a personal computer to output image data or information on a recording paper. Typically, the personal computers are connected to a single printer so that the personal computer is connected to the printer on a one to one basis. A centronics interface is the most popular way to connect a printer to a personal computer. Normally, the printer is connected to the personal computer via a connector conforming to the centronics standards.
There are many types of printers such as laser printers, inkjet printers, etc. Additionally, there are also monochrome and color types of printers. Demand for use of different types of printers with a single personal computer has been increasing. A description will now be given of a typical case in which a monochrome laser printer and a color inkjet printer are available. If only the monochrome laser printer is connected to a personal computer, the need for color printing cannot be satisfied. Thus, it is also desirable to have a color inkjet printer connected to the personal computer. On the other hand, if only the color inkjet printer is connected to the personal computer, although monochrome printing can be performed as well as color printing by the color inkjet printer, this does have its disadvantages. For example, monochrome printing by a color inkjet printer has a disadvantage in that the printing speed is much slower than that of the monochrome laser printer. Additionally, the image quality of monochrome printing performed by the color inkjet printer is much lower than that of the monochrome laser printer. Accordingly, considering the fact that most printing operations are require monochrome printing, it is preferable that the monochrome printer also be connected to the personal computer.
In most cases, when two printers are commonly used with one personal computer, the user must change from one printer to the other printer by disconnecting the centronics connector of one printer and connecting the centronics connector of the other printer. This changing operation is very inconvenient for the user.
In order to eliminate such inconvenience, a switching device 101 such as shown in FIG. 1 is commercially available. The switching device 101 is provided with three connectors CN1, CN2 and CN3 so that a personal computer 102 and two printers 103 and 104 are interconnected via the switching device 101. The switching device 101 is provided to selectively connect one of the printers 103 and 104 to the personal computer 102 by control of the personal computer 102. Accordingly, the switching device 101 is intended to eliminate the disconnecting and connecting operations of the connectors of the printers 103 and 104. However, the switching operation performed by the switching device 101 lacks reliability at the present time. This may be caused by poor compatibility between the personal computer 102 and printers 103 and 104. More specifically, although the personal computer 102 and the printers 103 and 104 have an interface conforming to the centronics standard, each of the interfaces may actually conform to various local standards which are based on the centronics standard. This situation creates a problem that a personal computer may not have compatibility with a particular printer. When the above-mentioned switching device 101 is used, as viewed from the personal computer 102, it is not recognizable as to what types of printers are connected to the switching device 101.
In order to eliminate the above-mentioned problem with respect to compatibility, the printers to be connected to the switching device 101 must be limited to ones which are compatible with the personal computer 102. Accordingly, the types of printers which can be connected to the switching device 101 is limited. This results in poor reliability of the switching function of the switching device 101. That is, since generally the personal computer is not intended to be used with two printer drivers, there may be a case in which the printer is not operatively connected to the personal computer. Additionally, even if the printers 102 and 104 can be operatively connected to the personal computer 102 via the switching device 101, the total length of the cables between the personal computer 102 and each of the printers 103 and 104 becomes excessively long, resulting in an increased possibility of noise intrusion. Further, the commercially available switching device 101 may perform a switching operation which requires electrical power which cannot be provided from the personal computer 102 via the connecter C1.
That is, there may be a case in which the switching device 101 must be directly connected to an external power source.
In the above-mentioned case, the personal computer 102 described as being connected to the printers 103 and 104. However, one or both of the printers 103 and 104 may be replaced by a multi-function image processing apparatus such as a multi-function peripheral (MFP) device which may include a facsimile function, a scanning function and a printing function. This results in similar problems to those discussed above.